Far Cry 2: Had absolutely nothing to do with the first one, and it was just boring to me.

Left 4 Dead 2: I had a lot of fun, and it exceeded my expectations. The problem was, after 150 hours of L4D1, I just got bored. Stopped at about 30 hours.

Fallout 3: I loved it when I got it (well, still do, I put a lot of time into it), so I am retroactively disappointed that it wasn't Van Buren. It did get me into the franchise, but after playing the first 2 games, it just doesn't do them justice. I felt like New Vegas mostly made up for it though.